An argument over a billing issue escalated into a stabbing this week when a clerk at a T-Mobile store allegedly attacked a customer as he was leaving the Pennsylvania store.

Police said store employee Darnell Schoolfield, 21, of Philadelphia, reportedly fled the area after the incident, according to the Daily Times. On Thursday, he was arrested at a Delaware hotel.

Upper Darby Police Superintendent Michael Chitwood told ABC 6 that the argument became physical quickly. At one point, the customer appeared to rip the name tag off Schoolfield. The assault was captured on camera.

“As the victim is going out of the store after the altercation, you can see store clerk stab him in the side,” Chitwood said.

However, the customer did not realize he had been stabbed until after he had driven himself to the police station to file an assault complaint.

“During the course of filing the complaint, he realizes he’s bleeding profusely from the left side of the stomach,” Chitwood said, according to the Philadelphia Daily News. “He’d thought he was just punched.”

Delaware County Memorial Hospital paramedics transported the victim to the Hospital of the University of Pennsylvania in Philadelphia, where he was admitted in critical condition, the Mercury reports. He underwent emergency surgery for the stab wound and is recovering.